Laminated materials such as, for example, composites are widely utilized to increase structural rigidity in a wide variety of products. For example, composites are generally utilized by the airplane construction industry to build structural members of airframes. In some of the most advanced aircraft, where high strength and rigidity and low weight are extremely important, composites may account for a significant portion of the airframe as well as the external surface or skin. Typically, these composites are constructed from a plurality of layers placed over a form. These layers are often referred to as partial or full plies. For structures exceeding the available material width, each layer is typically made up of a series of strips or courses of material placed edge to edge next to each other. Each ply may be in the form of woven fibers in a fabric, unidirectional fiber material or a variety of other conformations. Unidirectional fiber material is often termed, “tape.” The fibers may be made from any of a multitude of natural and/or “man-made” materials such as fiberglass, graphite, Kevlar®, and the like.
While these plies may simply include the above described fibers, generally the plies are pre-impregnated with a resin. Resins are typically formulated to allow the ply to adhere to the form as well as to previously applied plies. If some plies do not adequately adhere to their respective substrate, such as the previously applied plies or the form, internal and/or external surface imperfections. Accordingly, in order to facilitate proper adhesion, pressure is typically applied to the plies during and/or after ply placement.
For relatively small items, a press may be employed. For example, some known presses utilize a vacuum debulking table. In such arrangements, following placement of the plies, the part, referred to as a layup, is placed on the debulking table, a membrane is placed over the layup, and a pump is employed to remove the air from the layup. As the layup is depressurized, a compressive force is applied by the atmospheric pressure and air within the layup is removed. However, as the size of the layup increases and/or permeability of the layup decreases, the use of debulking tables tends to become undesirably expensive and cumbersome.
For relatively larger items, a rolling press may be employed. For example, in some known rolling presses, tape is dispensed from a dispensing head and then pressed on the substrate surface with a compaction roller. While the exact amount of force exerted by the roller depends upon a variety of factors, 100 Kg or more is often utilized in certain applications. In order to exert this relatively large force while accurately placing plies, substantial support and guidance structures are generally required. Another disadvantage of such known rolling presses is that a correspondingly substantial support is required for the form in order to withstand the force exerted by the roller. These and other disadvantages associated with the relatively large forces employed by rolling press systems greatly increase the costs of producing composite items.
Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent.